Devlopment of 270 VDC
Devlopment of 270 VDC
(OP)
In working with military aircraft power systems, I've come across 270 VDC systems before. Where does the decision to go with 270 VDC come from?
I had heard that it was derived from using 3 phase 400 hz 115/200 VAC power but I'm not sure how do the conversion to get 270 VDC.
I had heard that it was derived from using 3 phase 400 hz 115/200 VAC power but I'm not sure how do the conversion to get 270 VDC.





RE: Devlopment of 270 VDC
TTFN
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RE: Devlopment of 270 VDC
"+\- 270V (540V) supply as opposed to a 0-270V supply".
thread2-168599: +/- 270V (540V) supply as opposed to a 0 - 270V supply
RE: Devlopment of 270 VDC
The RMS value of 115 VAC is 115*.707= ~81 VDC. How do three phases of 81VDC lead to 270VDC? I know I'm missing something, but the previous entries to not adequately explain the conversion.
RE: Devlopment of 270 VDC
With a steady voltage input, a transformer/rectifier could do this. We use TR's to convert 115VAC to 28VDC so why not 270VDC. It probably wouldn't be efficient.
Most likely, the generator system is designed to output 270VDC. Generator with a power converter. Less weight because the gen does not need a CSD and associated controls. The power converter outputs a constant 270VDC from the variable generator input.
RE: Devlopment of 270 VDC
I was also wondering where the decision to use 270VDC came from. Sure the current goes down as you increase voltage, but why not use the rectified 3-phase AC voltage directly? Then you wouldn't need a transformer/rectifier (you could just use a rectifier) and could still have the higher VDC to keep the current down.
RE: Devlopment of 270 VDC
RE: Devlopment of 270 VDC
Your calculation is only for single phase. You need to calculate for 3 phase.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Devlopment of 270 VDC
RE: Devlopment of 270 VDC
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Devlopment of 270 VDC
While unbalanced line to line loads are discouraged, when I was working electrical power systems at Boeing, the window heat controller manufacturers plead for (and received) an exception to this rule. Being some of the largest electrical loads on the airplane, they messed up our attempts at maintaining load balance across phases.